CN112011029A - Polycarbonate-based end-capped polyurethane prepolymer, preparation method and application - Google Patents

Polycarbonate-based end-capped polyurethane prepolymer, preparation method and application Download PDF

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CN112011029A
CN112011029A CN202010775903.2A CN202010775903A CN112011029A CN 112011029 A CN112011029 A CN 112011029A CN 202010775903 A CN202010775903 A CN 202010775903A CN 112011029 A CN112011029 A CN 112011029A
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polyol
polyurethane prepolymer
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prepolymer
cyclocarbonate
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张炜
刘宇星
赵世琦
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Langfang Jindao Qishi Plastic Industry Co ltd
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Langfang Jindao Qishi Plastic Industry Co ltd
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    • C08G18/40—High-molecular-weight compounds
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    • C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
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    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
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Abstract

The invention provides a polycarbonate-group-terminated polyurethane prepolymer and a preparation method and application thereof, wherein the polyurethane prepolymer is completely terminated by a cyclic carbonate group, and the preparation method comprises the steps of respectively dehydrating polyol and a sealant, mixing the polyol and isocyanate, adding a catalyst, stirring, and carrying out prepolymerization reaction to obtain a polymer with an end group of an isocyanate group; then adding a sealing agent subjected to dehydration treatment to obtain a cyclocarbonate-based end-capped polyurethane prepolymer; finally, adding an active diluent to reduce the viscosity of the prepolymer according to the requirement. The polyurethane prepolymer disclosed by the invention has good flexibility, the anti-cracking performance, the impact resistance and the adhesive force of the epoxy resin are improved when a small amount of the polyurethane prepolymer is added into the epoxy resin, the flexibility is improved when a large amount of the polyurethane prepolymer is added, the cohesive strength and the hydrolysis resistance of a cured product are improved at the same time, and a small-molecule sealant is not released; the three wastes are not generated in the preparation process of the prepolymer, high temperature and high pressure are not needed, the requirements on the safety of production equipment and process control are lower, and the method is suitable for industrial production.

Description

Polycarbonate-based end-capped polyurethane prepolymer, preparation method and application
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to a polycarbonate-based end-capped polyurethane prepolymer, a preparation method and application thereof.
Background
Epoxy resin is a thermosetting resin with good bonding, corrosion resistance, insulation, high strength and other properties, is widely applied to the preparation of various materials such as adhesives, sealing materials, coatings, composite materials and the like, and is an indispensable basic material in various industrial fields. The cured product of the epoxy resin is usually a three-dimensional network structure with higher crosslinking density, is in a glass state at normal temperature, is generally hard and brittle, and has poor cracking resistance and impact resistance, so that the epoxy resin can be widely applied only after the toughness is improved. In the conventional method for improving the toughness, inactive plasticizers such as dibutyl phthalate, dioctyl phthalate and the like are usually used to soften a cured resin, so that the performance is improved to a certain extent, but the plasticizer slowly migrates to the surface of the cured resin with time, so that the toughness of the cured resin is reduced.
The addition of a proper toughening agent in an epoxy resin curing system can improve the cracking resistance and the impact resistance, and meanwhile, in some application fields, repair materials and surface protection materials of hydraulic buildings, encapsulating materials of the electronic industry and the like, a cured product is required to keep elasticity within a certain temperature range.
Chinese patents with publication numbers CN107973922A and CN101050344A adopt modified fully vulcanized powdered rubber to toughen and modify epoxy resin. The powdered rubber is prepared by irradiating and vulcanizing latexes such as styrene-butadiene rubber, carboxylic styrene-butadiene rubber, nitrile rubber, carboxylic nitrile rubber, polybutadiene rubber, chloroprene rubber, silicon rubber, acrylate rubber, butadiene-styrene-pyridine rubber and the like, the average particle size of the prepared powdered rubber product is in a nanometer level, the powdered rubber product is uniformly dispersed in epoxy resin, so that the toughness of a cured product is greatly improved, the heat resistance is not reduced or even improved, the prepared adhesive can obtain high tensile shear strength, high peel strength and high impact strength, but the requirement of the prepared powdered rubber on a dispersion process is higher, and an elastic epoxy resin cured product cannot be obtained.
The Chinese patent applications with the publication numbers of CN101445583A and CN101528802A and the Chinese patent of CN101528799B are that firstly, a polyurethane prepolymer intermediate with a terminal isocyanate-NCO group and polyether diol as flexible chains is prepared, and then a blocking agent with a hydroxyl-OH group and an epoxy group in a molecule is adopted to react to obtain the epoxy-terminated polyurethane modified epoxy resin which is used for an adhesive and a composite wear-resistant coating material and can enable a product to have high adhesive strength and high impact toughness.
In chinese patent publication No. CN103180400B, a prepolymer intermediate of polyurethane with a terminal isocyanate-NCO group and a flexible polyol as a main chain is prepared, and then the terminal isocyanate-NCO group is blocked by a phenolic compound, so that a structural adhesive with good lap shear and impact peel strength can be formed when the prepolymer is used in an epoxy resin curing system, but the phenolic blocked prepolymer of polyurethane is substituted by amino groups during the reaction with a curing agent having amino groups, thereby releasing small phenolic molecules.
Currently, the toughness and elasticity of epoxy resins can also be improved by non-isocyanate polyurethane materials. The Chinese patent application with publication number CN103013323A adopts CO2Gas and bisphenol F type epoxy resin are used as raw materials, epoxy groups are partially converted into cyclic carbonate groups under the conditions of heating, high pressure and catalyst, a part of epoxy groups are remained, thus mixed oligomers with cyclic carbonate groups and epoxy groups are obtained, and then the mixed oligomers react with amine-terminated polyether to obtain the epoxy non-isocyanate polyA polyurethane heavy-duty anticorrosive coating. The Chinese patent application with publication number CN101260232A adopts CO2Gas and epoxidized soybean oil are used as raw materials, epoxy groups are converted into cyclic carbonate groups under the conditions of heating high pressure and weak base catalyst, and then primary amine compounds are added after the epoxy groups are mixed with epoxy resin to cure the mixed resin, so that the mixed non-isocyanate polyurethane is obtained. However, the above technical solutions are all to mix the raw material with more than two epoxy groups with CO2The cyclic carbonate oligomer is reacted and converted into cyclic carbonate oligomer, and then the cyclic carbonate oligomer is mixed with common epoxy resin and then is cured by primary amine compounds to obtain the epoxy resin/non-isocyanate polyurethane mixed material. The preparation of the oligomer with the cyclic carbonate group needs to be carried out under high pressure, has higher requirements on the safety of production equipment and process control, and brings certain difficulty to industrialization.
Disclosure of Invention
The embodiment of the invention aims to improve the toughness and elasticity of an epoxy resin cured product, simplify the process, realize controllable industrial production without high-pressure gas and high-pressure resistant production equipment, and provide a polycarbonate-group-terminated polyurethane prepolymer, a preparation method and application.
In order to achieve the above purpose, the technical solution adopted by the embodiment of the present invention is as follows:
in a first aspect, embodiments of the present invention provide a polycarbonate-based end-capped polyurethane prepolymer, where the polyurethane prepolymer is fully end-capped with a cyclic carbonate group.
As a preferred embodiment of the present invention, the prepolymer has the following structural formula:
Figure BDA0002618396690000031
wherein the content of the first and second substances,
R1represents a small molecule or a large molecule chain segment contained in the polyol except for the terminal hydroxyl;
R2represents alkyl or cycloalkyl or aryl or aralkyl contained in isocyanate;
R1and R2At least one NCO group;
subscript n represents the number of repeating units contained in the generated prepolymer;
the two-sided five-membered rings represent cyclic carbonate groups.
As a preferred embodiment of the present invention, the polyol is one or a mixture of two or more of small molecule polyol, polyether polyol, polyester polyol, polyolefin polyol and vegetable oil polyol;
the isocyanate is diisocyanate or polyisocyanate.
In a second aspect, an embodiment of the present invention further provides a preparation method of a polycarbonate-based end-capped polyurethane prepolymer, where the preparation method uses raw materials including: polyol, diisocyanate or polyisocyanate, a blocking agent containing cyclic carbonate groups and hydroxyl groups in a molecule at the same time, and a catalyst;
the mass percentage of the raw materials is as follows:
Figure BDA0002618396690000032
the preparation method comprises the following steps:
step A, respectively dehydrating polyhydric alcohol and a sealing agent under the conditions of vacuum and heating;
step B, mixing polyol and diisocyanate or polyisocyanate according to a preset molar ratio, stirring at a first preset temperature under the protection of atmosphere for prepolymerization reaction, adding a catalyst, stirring at a second preset temperature for prepolymerization reaction, and obtaining a polymer with an end group of isocyanate-NCO;
and C, adding a dehydrated blocking agent into the polymer obtained in the step B to obtain a polymer which does not contain-NCO groups and has a terminal group of a cyclocarbonate group.
As a preferred embodiment of the present invention, the raw materials adopted by the preparation method further include: and C, a chain extender, wherein the chain extender accounts for 1-5% of the total mass percentage, and the chain extender is added before the addition of the sealing agent in the step C.
As a preferred embodiment of the present invention, the raw materials adopted by the preparation method further include: the active diluent accounts for 0-30% of the total mass; the preparation method further comprises the following steps: and D, adding an active diluent into the polymer obtained in the step C and stirring to obtain a cyclocarbonate-based end-capped polyurethane prepolymer.
As a preferred embodiment of the present invention, the polyol is one or a mixture of two or more of small molecule polyol, polyether polyol, polyester polyol, polyolefin polyol, and vegetable oil polyol.
As a preferred embodiment of the present invention, the small molecule polyol includes trimethylolpropane, glycerol, trimethylolethane, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, sucrose, sorbitol, pentaerythritol, triethanolamine, diethanolamine;
the polyether polyol comprises polyoxypropylene polyol PPG with the average molecular weight of more than 400, polyoxyethylene polyol PEG, polyoxybutylene polyol, polymer polyol, polytetrahydrofuran PTMEG and polyether polyol copolymer;
the polyester polyol comprises conventional polyester polyol with the average molecular weight of more than 400, polycaprolactone polyol and polycarbonate diol;
the polyolefin polyol comprises hydroxyl-terminated polybutadiene HTPB with the average molecular weight of more than 400, hydroxyl-terminated polybutadiene-acrylonitrile HTBN, hydroxyl-terminated styrene-butadiene liquid rubber and hydrogenated hydroxyl-terminated polybutadiene;
the vegetable oil polyol comprises castor oil polyol, soybean oil polyol and palm oil polyol.
As a preferred embodiment of the present invention, the di-or polyisocyanate is selected from one or more of toluene diisocyanate TDI, diphenylmethane diisocyanate MDI or liquefied MDI, isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, dicyclohexylmethane diisocyanate HMDI, xylylene diisocyanate XDI and polymethylene polyphenyl isocyanate PAPI.
As a preferred embodiment of the present invention, the blocking agent containing a cyclic carbonate group and a hydroxyl group is glycerol carbonate GC.
In a third aspect, an embodiment of the present invention further provides an application method of a polycarbonate-based end-capped polyurethane prepolymer, where the polyurethane prepolymer according to any one of claims 1 to 3 is applied to toughening of an epoxy resin.
The embodiment of the invention has the following beneficial effects:
(1) the cyclocarbonate-terminated polyurethane prepolymer is completely terminated by cyclocarbonate, can be stably stored, is simple and easy to use as an epoxy resin toughening agent, and can introduce the conventional isocyanate polyurethane soft and hard chain segment into an epoxy resin matrix so as to combine the advantages of polyurethane resin and epoxy resin;
(2) the preparation process of the cyclocarbonate group-terminated polyurethane prepolymer is simple, the cyclocarbonate group can be introduced into an epoxy resin curing system only by a conventional production process and common production equipment, and special high-pressure-resistant production equipment and high-pressure CO (carbon monoxide) are not required2A gas;
(3) when the cyclocarbonate-based end-capped polyurethane prepolymer is applied as a toughening agent, a sea-island structure is formed in a cured product when a small amount of cyclocarbonate-based end-capped polyurethane prepolymer is added, the anti-cracking performance, the impact resistance and the bonding force are effectively improved, an elastic epoxy resin cured product with excellent elasticity is obtained when a large amount of cyclocarbonate-based end-capped polyurethane prepolymer is added, and the hardness degree of the cured product can be flexibly adjusted through formula adjustment; meanwhile, the prepolymer is reacted with a primary amine curing agent through cyclic carbonate to generate a non-isocyanate polyurethane unit with intramolecular hydrogen bonds, and the novel non-isocyanate polyurethane unit can effectively improve the cohesive strength and hydrolysis resistance of a cured product and does not release a small-molecule sealant.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is an infrared spectrum of a cyclocarbonate-based end-capped polyurethane prepolymer in an embodiment of the present invention.
Detailed Description
The technical problems, aspects and advantages of the invention will be explained in detail below with reference to exemplary embodiments. The following exemplary embodiments are merely illustrative of the present invention and are not to be construed as limiting the invention. It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The embodiment of the invention provides a polycarbonate-group-terminated polyurethane prepolymer based on toughening of epoxy resin, and a preparation method and application thereof. The polyurethane is a high molecular compound formed by reacting organic polyisocyanate and polyhydroxy compound, wherein the non-isocyanate polyurethane refers to polyurethane synthesized by taking no isocyanate as a raw material, and is called NIPU for short. NIPU can be prepared by reacting a cyclic carbonate oligomer with a primary amine species to form a beta-hydroxy carbamate. Hydroxyl in the beta-hydroxy carbamate can form a seven-membered ring with carbonyl through intramolecular hydrogen bond, and the formula (1) is a reaction formula for forming intramolecular hydrogen bond. The existence of the intramolecular hydrogen bond improves the hydrolysis resistance of the polyurethane material, and the chemical resistance of the material is 1.5-2 times higher than that of a material which has the same chemical structure and does not contain the intramolecular hydrogen bond.
Figure BDA0002618396690000061
The cyclic carbonate oligomers used to prepare the NIPU are generally epoxy resins, especially bisphenol a type epoxy resins, and also CO2The gas is used as raw material, epoxy groups at two ends of the gas are converted into cyclic carbonate groups under the condition of heating and high pressure with a catalyst, and then the amino-terminated polyether with a flexible chain reacts with the oligomer with the cyclic carbonate groups to generate the non-isocyanate polyurethane material NIPU. The invention provides a method for preparing cyclic carbonate-terminated polyurethane prepolymer by using polyol, chain extender, diisocyanate (or polyisocyanate), sealant containing cyclic carbonate group and hydroxyl group in molecule and trace catalyst as starting materials, and cyclic carbonate-terminated polyurethane prepolymer and application thereof in order to overcome the limitation of production conditions such as heating high pressure with catalyst and the like. The polyurethane prepolymer is completely terminated by a cyclocarbonate group, and the formula (2) is the structural formula of the prepolymer.
Figure BDA0002618396690000062
Wherein the content of the first and second substances,
R1represents a small molecule or a large molecule chain segment contained in the polyol except for the terminal hydroxyl;
R2represents alkyl or cycloalkyl or aryl or aralkyl contained in isocyanate;
R1and R2At least one NCO group;
subscript n represents the number of repeating units contained in the generated prepolymer;
the two-sided five-membered rings represent cyclic carbonate groups.
In the preparation process of the polyurethane prepolymer, the components and the mass percentage of each raw material are as follows: 25-95% of polyol, 3-45% of diisocyanate (or polyisocyanate), 1-30% of a sealant containing cyclic carbonate groups, 0-30% of a reactive diluent and less than 1% of a catalyst; in addition, the chain extender can be added by 0-5%.
The preparation process of the polyurethane specifically comprises the following steps:
step A, respectively carrying out pre-dehydration treatment on the used raw material polyol, the chain extender and the sealing agent containing cyclic carbonate groups and hydroxyl groups, wherein the dehydration process is carried out under the conditions of preset vacuum degree and heating and stirring process.
Preferably, the relative vacuum degree of the pre-dehydration process reaches more than-0.08 MPa, and the heating and stirring temperature is more than 80 ℃; more preferably, the relative vacuum degree of the pre-dehydration process reaches more than-0.09 MPa, and the heating and stirring temperature is more than 110 ℃.
And step B, feeding the dehydrated polyol and diisocyanate (or polyisocyanate) according to the designed molar ratio of the isocyanate group content and the hydroxyl group content of the raw materials, preferably, the molar ratio is 2:1 or 3:2, and ensuring that the isocyanate group in the system is excessive. Heating to a preset temperature, stirring under the protection of atmosphere, carrying out prepolymerization reaction, sampling and detecting in the reaction process, and stopping the reaction when the content of NCO% of a reaction product reaches a preset value to prepare a prepolymer with an end group of-NCO. The predetermined value is preferably a theoretical value. To ensure adequate prepolymerization, less than 1% of catalyst is added during the reaction.
The prepolymerization temperature in this step is preferably 50 ℃ to 90 ℃, more preferably 60 ℃ to 80 ℃, and the reaction time is preferably 4 to 6 hours. The catalyst is added during the reaction, preferably less than 0.2% of an organometallic catalyst is added, more preferably less than 0.1% of an organotin-based catalyst is added. After the catalyst is added, the stirring temperature is correspondingly adjusted according to the actual situation. The atmosphere protection is inert gases such as argon, nitrogen and the like.
And C, adding 0-5% of dehydrated micromolecule chain extender on the basis of the prepolymer in the step B according to the product requirement to adjust the chain segment structure and the-NCO group content and increase the molecular weight of the prepolymer. The chain extension reaction can be carried out as required, the addition amount of the dehydrated micromolecule chain extender is preferably 0-2%, the chain extension reaction temperature is preferably 60-80 ℃, and the chain extension reaction time is preferably 1-2 hours.
And (C) adding 1-30% of a sealing agent containing dehydrated cyclocarbonate groups into the chain-extended prepolymer or the prepolymer obtained in the step (B), wherein hydroxyl groups carried by the sealing agent react with residual terminal-NCO groups of the prepolymer obtained in the previous step to obtain a polymerization product which does not contain-NCO groups (is completely sealed) and has terminal groups of cyclocarbonate groups, namely the cyclocarbonate group-terminated polyurethane prepolymer.
The blocking agent containing cyclic carbonate groups is preferably glycerol carbonate GC, the addition amount of the blocking agent is preferably 5-15%, the blocking reaction temperature is preferably 60-90 ℃, and the blocking reaction time is preferably 1-3 hours.
In order to reduce the viscosity of the polymerization product obtained in step C, the embodiment of the present invention may further include: and D, adding a low-viscosity reactive diluent after the step C is finished, and fully and uniformly stirring to finally obtain the cyclocarbonate-based end-capped polyurethane prepolymer.
The low-viscosity reactive diluent is preferably a glycidyl ether compound, the addition amount is preferably 10-20%, the temperature in the stirring and diluting process is preferably 60-90 ℃, and the stirring time is preferably 0.5-2 hours.
The polyol in the step A is one or a mixture of two or more of polyols such as micromolecular polyol, polyether polyol, polyester polyol, polyolefin polyol, vegetable oil polyol and the like.
The small molecule polyols include trimethylolpropane, glycerol, trimethylolethane, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, sucrose, sorbitol, pentaerythritol, triethanolamine, diethanolamine, and the like, and alkoxylates thereof having a molecular weight of at most 599, especially at most 500.
The polyether polyol comprises polyoxypropylene (propylene oxide) polyol PPG with the average molecular weight of more than 400, polyoxyethylene (ethylene oxide) polyol PEG, polyoxybutylene (butylene oxide) polyol, polymer polyol, polytetrahydrofuran PTMEG and polyether polyol copolymer thereof and the like.
The polyester polyol comprises conventional polyester polyol (hydroxyl-terminated polymer obtained by polycondensation of dicarboxylic acid or carboxylic anhydride and dihydric alcohol) with average molecular weight of above 400, polycaprolactone polyol, polycarbonate diol, etc.
The polyolefin polyol comprises hydroxyl-terminated polybutadiene HTPB with the average molecular weight of more than 400, hydroxyl-terminated polybutadiene-acrylonitrile HTBN, hydroxyl-terminated styrene-butadiene liquid rubber, hydrogenated hydroxyl-terminated polybutadiene and the like.
The vegetable oil polyol includes castor oil polyol, soybean oil polyol, palm oil polyol and the like.
Other polyols also include polyacrylate polyols, rosin ester polyols, fatty acid dimer diols, polyether ester diols, and the like.
The polyol used is preferably one or a mixture of two of a polyether polyol and a polyolefin polyol having an average molecular weight of 400 or more, more preferably one or a mixture of two of a polyether polyol and a polyolefin polyol having an average molecular weight of 1000 or more.
The chain extender in the step C is one or a mixture of more than one of 1, 4-butanediol, diethylene glycol, 1, 3-propanediol, 2-methyl-1, 3-propanediol, neopentyl glycol, dichlorodiphenylmethanediamine MOCA, diethyltoluenediamine DETDDA, dimethylthiotoluenediamine DMTDA and the like. The chain extender is preferably one or a mixture of two of small molecular weight dihydric alcohols such as 1, 4-butanediol, 1, 3-propanediol and the like.
The diisocyanate (or polyisocyanate) is selected from toluene diisocyanate TDI, diphenylmethane diisocyanate MDI (containing liquefied MDI), isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, dicyclohexylmethane diisocyanate HMDI, xylylene diisocyanate XDI, polymethylene polyphenyl isocyanate PAPI and the like. Preference is given to toluene diisocyanate TDI, liquefied MDI diphenylmethane diisocyanate and isophorone diisocyanate IPDI.
The blocking agent containing cyclic carbonate groups is selected from glycerol carbonate GC or other compounds with both cyclic carbonate and hydroxyl in the molecular structure. Preferred is glycerol carbonate GC.
The catalyst is selected from tertiary amine catalysts (including quaternary ammonium salts thereof) and catalysts used in the polyurethane industry such as organic metal compounds, tertiary amine catalysts such as N, N-dimethylcyclohexylamine, triethylamine, N-dimethylbenzylamine, triethylenediamine, N' -diethylpiperazine, N-methylmorpholine and the like, and organic metal compounds such as dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, zinc isooctoate, bismuth isooctanoate and the like. Preference is given to dibutyltin dilaurate, stannous octoate and bismuth isooctanoate.
The reactive diluent in step D is selected from monofunctional glycidyl ether compounds, such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, C12-14 alkyl glycidyl ether and the like, bifunctional glycidyl ether compounds, such as ethylene glycol diglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether and the like, multifunctional glycidyl ether compounds, such as glycerol polyglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether and the like, glycidyl ester compounds, such as tert-glycidyl carbonate, adipic acid diglycidyl ester, dimer acid diglycidyl ester and the like, glycidyl amine compounds, such as diglycidyl aniline and the like, small molecular cyclic carbonate compounds capable of reacting with amines, such as vinyl carbonate, vinyl ester compounds, and the like, Propylene carbonate and glycerol carbonate GC, etc.
As an embodiment of the invention, the prepared polyurethane prepolymer is applied to curing and toughening of epoxy resin, and the process of toughening the epoxy resin comprises the steps of adding a small amount of prepolymer and adding a large amount of prepolymer. The small amount of the epoxy resin is 1 to 30 percent of the weight of the epoxy resin; the large amount of the epoxy resin is 50 to 90 percent of the weight of the epoxy resin. When a small amount of the epoxy resin is added, the cracking resistance, the impact resistance and the binding power of the epoxy resin are improved, and when a large amount of the epoxy resin is added, the flexibility of the epoxy resin is improved, so that an elastic epoxy resin cured product with excellent elasticity is obtained. The prepared cyclocarbonate-based end-capped polyurethane prepolymer is used as a novel epoxy resin toughening agent to be applied to an epoxy resin formula cured by a primary amine curing agent, is mixed with epoxy resin, and simultaneously generates a ring-opening reaction with the primary amine curing agent in the epoxy resin curing process to form a PU-EP interpenetrating network, so that excellent performance is brought to the epoxy resin formula. The epoxy resin cured product prepared by using the cyclocarbonate-terminated polyurethane prepolymer as the toughening agent has high flexibility, and an elastomer material with excellent flexibility (elasticity) can be obtained when the addition amount is large.
The polyurethane prepolymer disclosed by the embodiment of the invention is simple and convenient in preparation process, does not need high-temperature and high-pressure conditions, does not generate three wastes, is good in environmental protection performance and excellent in storage and transportation stability, and can be used for obtaining a product with 100% solid content or high solid content. The prepolymer is synchronously reacted with the primary amine curing agent with the epoxy resin during curing, the polyurethane prepolymer with good flexibility is introduced into the cured epoxy resin to form a PU-EP interpenetrating network (IPN), the flexibility of the epoxy resin is improved, and a non-isocyanate polyurethane unit with an intramolecular hydrogen bond is further generated through the reaction of the cyclic carbonate and the primary amine curing agent, the novel non-isocyanate polyurethane unit further improves the cohesive strength and hydrolysis resistance of the cured product, and the release problem of a sealing agent is avoided in the process.
The present invention will be described in further detail with reference to specific examples.
Example 1
This example provides a polycarbonate-based end-capped polyurethane prepolymer that is fully end-capped with a cyclic carbonate.
The preparation process of the polyurethane prepolymer is as follows:
step A, respectively heating and dehydrating polypropylene oxide polyether polyol PPG1000 (average molecular weight is 1000, functionality is 2) and glycerol carbonate GC in a three-neck flask with a stirrer, starting a vacuum pump after the temperature of a heated material reaches 110 ℃, keeping the vacuum degree above-0.09 MPa, dehydrating for 2 hours, cooling and sealing for later use.
And step B, another three-neck flask with the capacity of 1 liter is taken, 400g (0.4mol) of dewatered PPG1000 is accurately weighed and placed into the three-neck flask, 139.2 g of toluene diisocyanate TDI-80(0.8mol) is added immediately, the mixture is placed into a 60 ℃ oil bath for heating and stirring reaction, dry nitrogen is introduced for protection in the reaction process, the temperature of the oil bath is raised to 80 ℃ after the reaction is carried out for 3 hours at 60 ℃, 0.32g of dibutyltin dilaurate catalyst is added in the heating process, and the reaction is continued for 2 hours at 80 ℃ to ensure that the prepolymer with terminal-NCO groups is generated.
And C, continuously adding 94.4g of dehydrated glycerol carbonate GC (0.8mol) into the prepolymer obtained in the step B to perform NCO group sealing reaction, and continuously reacting for 2 hours at 80 ℃ to generate a polymer with a terminal group of a cyclocarbonate group, namely the cyclocarbonate group-terminated polyurethane prepolymer.
And D, adding 64g of butyl glycidyl ether reactive diluent into the polymer obtained in the step C, and continuously stirring for 30min to obtain a cyclocarbonate group end-capped polyurethane prepolymer PU-GC 1.
FIG. 1 shows an infrared spectrum obtained by Fourier transform infrared spectrometer (FTIR) analysis of a cyclocarbonate-based end-capped polyurethane prepolymer PU-GC1 prepared in this example. As shown in FIG. 1, the infrared spectrum shows a strong absorption peak of five-membered ring of the cyclic carbonate group and a strong absorption peak of carbonyl group of the carbamate at 2273-2274cm-1And a characteristic peak of residual isocyanate groups does not exist nearby, so that the prepolymerization and the blocking reaction are complete, and a cyclocarbonate group-terminated polyurethane prepolymer is generated.
The embodiment also provides application of the cyclocarbonate-terminated polyurethane prepolymer, and the cyclocarbonate-terminated polyurethane prepolymer prepared in the embodiment is used for toughening epoxy resin. The toughening process for the epoxy resin comprises a small amount of addition and a large amount of addition. The small amount of the epoxy resin is 1 to 30 percent of the weight of the epoxy resin; the large amount of the epoxy resin is 50 to 90 percent of the weight of the epoxy resin.
The procedure for adding a small amount of the cyclocarbonate-based end-capped polyurethane prepolymer prepared in this example to a primary amine-cured epoxy resin system was as follows: the base resin is conventional bisphenol A epoxy resin E-51, the curing agent is a mixture of two primary amines and a small amount of phenolic accelerator, the specific proportion is m-xylylenediamine MXDA, polypropylene oxide ether diamine D-230, nonyl phenol 36:58:6 parts by weight, the curing agent is prepared by fully and uniformly mixing the two primary amines according to the proportion, and the mixture is named as curing agent MA 230. According to the epoxy resin E-51: and (3) fully and uniformly mixing the curing agent MA230 to 100:25 parts by weight to prepare the basic glue solution. On the basis of the formula of the glue solution, more than 10 parts of the cyclocarbonate-based end-capped polyurethane prepolymer PU-GC1 prepared in the embodiment is added to 100 parts of epoxy resin 128, and because the PU-GC1 prepolymer and a primary amine curing agent undergo a ring-opening reaction, the dosage of the curing agent is correspondingly increased. The specific toughening effect is shown by the notch impact toughness of the cast body and the data change of the steel-steel tensile shear test piece, and the formula and the test data are shown in table 1.
The procedure for adding a large amount of the cyclocarbonate-based end-capped polyurethane prepolymer prepared in this example to a primary amine-cured epoxy resin system was as follows: the base resin is conventional bisphenol A epoxy resin E-51, a small amount of reactive diluent C12-14 alkyl glycidyl ether is added in a formula for reducing viscosity, the curing agent is a mixture of two primary amines and a small amount of phenolic accelerators, the specific proportion is m-xylylenediamine MXDA, polypropylene oxide ether diamine D-230, nonyl phenol 36:58:6 parts by weight, the curing agent is prepared by fully and uniformly mixing the two primary amines according to the proportion, and the mixture is named as curing agent MA 230. The method comprises the steps of adding 10 parts of reactive diluent into 20 parts of epoxy resin 128, adding 70 parts of the cyclocarbonate-based end-capped polyurethane prepolymer PU-GC1 prepared in the embodiment, preparing mixed resin, and calculating the consumption of the mixed primary amine curing agent MA230 according to the equivalent of epoxy groups and cyclic carbonate groups participating in reaction contained in 100 parts of the mixed resin. The elasticity of the particular cured product is shown by the elongation at break of the dumbbell shaped cast body, and the formulations and test data are shown in table 2.
The cyclocarbonate-based end-capped polyurethane prepolymer has good flexibility, forms a 'sea-island structure' when the addition amount of the cyclocarbonate-based end-capped polyurethane prepolymer is small, improves the cracking resistance, the impact resistance and the binding power of epoxy resin, forms a PU-EP interpenetrating network IPN when the addition amount is large, improves the flexibility of the epoxy resin, obtains an elastic epoxy resin cured product with excellent elasticity, and can flexibly adjust the hardness of the cured product through the adjustment of the addition amount; simultaneously reacting cyclic carbonate with primary amine curing agent to generate non-isocyanic acid with intramolecular hydrogen bondEster polyurethane unit, further improve the cohesive strength and hydrolysis resistance of the cured product, and meanwhile, the small molecule sealant can not be released. The process of introducing the polycarbonate-terminated polyurethane prepolymer into the epoxy resin does not need special high-pressure-resistant production equipment and high-pressure CO2And the gas has lower requirements on the safety of production equipment and process control.
Example 2
This example provides a polycarbonate-based end-capped polyurethane prepolymer that is fully end-capped with a cyclic carbonate.
The preparation process of the polyurethane prepolymer is as follows:
step A, respectively heating and dehydrating polypropylene oxide polyether polyol PPG2000 (average molecular weight 2000, functionality 2) and glycerol carbonate GC in a three-neck flask with a stirrer, starting a vacuum pump after the temperature of a heated material reaches 110 ℃, keeping the vacuum degree above-0.09 MPa, dehydrating for 2 hours, cooling and sealing for later use.
And step B, taking another 1L three-neck flask, adding 400g (0.2mol) of dewatered PPG2000, accurately weighing, immediately adding 69.6 g of toluene diisocyanate TDI-80(0.4mol), putting the mixture into a 60 ℃ oil bath, heating and stirring for reaction, introducing dry nitrogen for protection in the reaction process, heating the oil bath to 80 ℃ after reacting for 3 hours at 60 ℃, adding 0.23g of dibutyltin dilaurate catalyst in the heating process, and continuing to react for 2 hours at 80 ℃ to ensure that an NCO group terminated prepolymer is generated by the reaction.
And step C, continuously adding 47.2g of dehydrated glycerol carbonate GC (0.4mol) into the prepolymer obtained in the step B to perform NCO group sealing reaction, and continuously reacting for 2 hours at 80 ℃ to generate a polymer with a terminal group of a cyclocarbonate group, namely the cyclocarbonate group-terminated polyurethane prepolymer.
And D, adding 52g of butyl glycidyl ether reactive diluent into the polymer obtained in the step C, and continuously stirring for 30min to obtain a cyclocarbonate group end-capped polyurethane prepolymer PU-GC 2.
In the infrared spectrogram of the cyclocarbonate-based end-capped polyurethane prepolymer prepared in the example, similar to FIG. 1, cyclic carbonate is includedThe strong absorption characteristic peak of the five-membered ring and the carbonyl strong absorption characteristic peak of the carbamate are respectively 2273-2274cm-1And a characteristic peak of residual isocyanate groups does not exist nearby, so that the prepolymerization and the blocking reaction are complete, and a cyclocarbonate group-terminated polyurethane prepolymer is generated.
The embodiment also provides application of the cyclocarbonate-terminated polyurethane prepolymer, and the cyclocarbonate-terminated polyurethane prepolymer prepared in the embodiment is used for toughening epoxy resin. The procedure was the same as in example 1, including small additions and large additions, with the corresponding formulations and test data for small additions being shown in Table 1 and the corresponding formulations and test data for large additions being shown in Table 2.
Example 3
This example provides a polycarbonate-based end-capped polyurethane prepolymer that is fully end-capped with a cyclic carbonate.
The preparation process of the polyurethane prepolymer is as follows:
step A, respectively heating and dehydrating polypropylene oxide polyether polyol PPG1000 (average molecular weight is 1000, functionality is 2) and glycerol carbonate GC in a three-neck flask with a stirrer, starting a vacuum pump after the temperature of a heated material reaches 120 ℃, keeping the vacuum degree to be more than-0.09 MPa, dehydrating for 2 hours, cooling and sealing for later use.
And step B, taking another 1L three-neck flask, putting 400g (0.4mol) of the dewatered PPG1000 into the three-neck flask, accurately weighing the three-neck flask, immediately adding 104.4 g of toluene diisocyanate TDI-80(0.6mol), putting the three-neck flask into a 60 ℃ oil bath, heating and stirring for reaction, introducing dry nitrogen for protection in the reaction process, heating the oil bath to 80 ℃ after reacting for 3 hours at 60 ℃, adding 0.25g of dibutyltin dilaurate catalyst in the heating process, and continuing to react for 2 hours at 80 ℃ to ensure that the prepolymer with the NCO groups is generated by reaction.
And step C, adding 47.2g of dehydrated glycerol carbonate GC (0.4mol) into the prepolymer in the step B to perform NCO group blocking reaction, and continuing the reaction at 80 ℃ for 2 hours to generate the polymer with the terminal group being a cyclocarbonate group.
And D, adding 83g of 1, 4-butanediol diglycidyl ether serving as an active diluent into the polymer obtained in the step C, and continuously stirring for 30min to obtain a cyclocarbonate-based end-capped polyurethane prepolymer PU-GC 3.
In the infrared spectrogram of the cyclocarbonate-terminated polyurethane prepolymer prepared in this example, the characteristic peak of strong absorption of five-membered ring with a carbonate group and the characteristic peak of strong absorption of carbonyl group with carbamate are within 2273-2274cm-1And a characteristic peak of residual isocyanate groups does not exist nearby, so that the prepolymerization and the blocking reaction are complete, and a cyclocarbonate group-terminated polyurethane prepolymer is generated.
The embodiment also provides application of the cyclocarbonate-terminated polyurethane prepolymer, and the cyclocarbonate-terminated polyurethane prepolymer prepared in the embodiment is used for toughening epoxy resin. The procedure was the same as in example 1, including small additions and large additions, with the corresponding formulations and test data for small additions being shown in Table 1 and the corresponding formulations and test data for large additions being shown in Table 2.
Example 4
This example provides a polycarbonate-based end-capped polyurethane prepolymer that is fully end-capped with a cyclic carbonate.
The preparation process of the polyurethane prepolymer is as follows:
step A, respectively heating and dehydrating polypropylene oxide polyether polyol PPG1000 (average molecular weight is 1000, functionality is 2), glycerol carbonate GC and chain extender 1, 4-butanediol in a three-neck flask with stirring, starting a vacuum pump after the temperature of a heated material reaches 110 ℃, keeping the vacuum degree above-0.095 MPa, dehydrating for 2 hours, cooling and sealing for later use.
And step B, taking another 1L three-neck flask, putting 400g (0.4mol) of dewatered PPG1000 accurately weighed in the three-neck flask, immediately adding 139.2 g of toluene diisocyanate TDI-80(0.8mol), putting the mixture into a 60 ℃ oil bath, heating and stirring for reaction, introducing dry nitrogen for protection in the reaction process, heating the oil bath to 80 ℃ after reacting for 3 hours at 60 ℃, adding 0.27g of stannous octoate catalyst in the heating process, and continuing to react for 2 hours at 80 ℃ to ensure that the prepolymer with the NCO groups is generated by the reaction.
Step C, adding 9g of dehydrated chain extender 1, 4-butanediol (0.1mol) into the prepolymer in the step B while keeping stirring, and continuing to react for 1 hour at the temperature of 80 ℃ to carry out the chain extension reaction of NCO groups; and (3) continuously adding 70.8g of dehydrated glycerol carbonate GC (0.6mol) into the prepolymer after the chain extension reaction is finished to carry out NCO group blocking reaction, and continuously reacting for 2 hours at 80 ℃ to generate the polymer with the end group being a cyclocarbonate group.
And D, adding 93g of reactive diluent C12-C14 alkyl glycidyl ether into the polymer obtained in the step C, and continuously stirring for 30min to obtain a cyclocarbonate-based end-capped polyurethane prepolymer PU-GC 4.
In the infrared spectrogram of the cyclocarbonate-terminated polyurethane prepolymer prepared in this example, the characteristic peak of strong absorption of five-membered ring with a carbonate group and the characteristic peak of strong absorption of carbonyl group with carbamate are within 2273-2274cm-1And a characteristic peak of residual isocyanate groups does not exist nearby, so that the prepolymerization and the blocking reaction are complete, and a cyclocarbonate group-terminated polyurethane prepolymer is generated.
The embodiment also provides application of the cyclocarbonate-terminated polyurethane prepolymer, and the cyclocarbonate-terminated polyurethane prepolymer prepared in the embodiment is used for toughening epoxy resin. The procedure was the same as in example 1, including small additions and large additions, with the corresponding formulations and test data for small additions being shown in Table 1 and the corresponding formulations and test data for large additions being shown in Table 2.
Example 5
This example provides a polycarbonate-based end-capped polyurethane prepolymer that is fully end-capped with a cyclic carbonate.
The preparation process of the polyurethane prepolymer is as follows:
step A, respectively heating and dehydrating polypropylene oxide polyether polyol PPG2000 (average molecular weight 2000, functionality 2), polytetrahydrofuran PTMEG2000 (average molecular weight 2000, functionality 2) and glycerol carbonate GC in a three-neck flask with a stirrer, starting a vacuum pump after the temperature of a heated material reaches 110 ℃, keeping the vacuum degree above-0.095 MPa, dehydrating for 2 hours, cooling and sealing for later use.
And step B, taking another 1L three-neck flask, putting 200g (0.1mol) of dewatered PPG2000 and 200g (0.1mol) of dewatered PTMEG2000 into the three-neck flask, immediately adding 100 g (0.4mol) of diphenylmethane diisocyanate MDI-50, putting the mixture into a 60 ℃ oil bath, heating and stirring for reaction, introducing dry nitrogen for protection in the reaction process, raising the temperature of the oil bath to 80 ℃ after reacting for 3 hours at 60 ℃, adding 0.25g of stannous octoate catalyst in the heating process, and continuing to react for 2 hours at 80 ℃ to ensure that the prepolymer with the NCO groups is generated by the reaction.
And step C, adding 47.2g of dehydrated glycerol carbonate GC (0.4mol) into the prepolymer in the step B to perform NCO group blocking reaction, and continuing the reaction at 80 ℃ for 2 hours to generate the polymer with the terminal group being a cyclocarbonate group.
And D, adding 82g of butyl glycidyl ether reactive diluent into the polymer obtained in the step C, and continuously stirring for 30min to obtain a cyclocarbonate group end-capped polyurethane prepolymer PU-GC 5.
In the infrared spectrogram of the cyclocarbonate-terminated polyurethane prepolymer prepared in this example, the characteristic peak of strong absorption of five-membered ring with a carbonate group and the characteristic peak of strong absorption of carbonyl group with carbamate are within 2273-2274cm-1And a characteristic peak of residual isocyanate groups does not exist nearby, so that the prepolymerization and the blocking reaction are complete, and a cyclocarbonate group-terminated polyurethane prepolymer is generated.
The embodiment also provides application of the cyclocarbonate-terminated polyurethane prepolymer, and the cyclocarbonate-terminated polyurethane prepolymer prepared in the embodiment is used for toughening epoxy resin. The procedure was the same as in example 1, including small additions and large additions, with the corresponding formulations and test data for small additions being shown in Table 1 and the corresponding formulations and test data for large additions being shown in Table 2.
TABLE 1
Figure BDA0002618396690000161
Note: the curing process is that after curing for 24 hours at normal temperature, the temperature is increased by 80 ℃ for 6 hours, and then the performance is tested after cooling.
TABLE 2
Figure BDA0002618396690000162
Note: the curing process is that after curing for 24 hours at normal temperature, the temperature is increased by 80 ℃ for 6 hours, and then the performance is tested after cooling.
The test data in Table 1 show that prepolymers of PU-GC1 to PU-GC-5 have obvious toughening effect after being added with a small amount of epoxy resin/primary diamine curing system. The test data in Table 2 show that the prepolymers of PU-GC1 to PU-GC-5 have obvious effect of improving the elasticity of the cured product after being added with a large amount of epoxy resin primary amine curing system.
While the foregoing is directed to the preferred embodiment of the present invention, it is understood that the invention is not limited to the exemplary embodiments disclosed, but is made merely for the purpose of providing those skilled in the relevant art with a comprehensive understanding of the specific details of the invention. It will be apparent to those skilled in the art that various modifications and adaptations of the present invention can be made without departing from the principles of the invention and the scope of the invention is to be determined by the claims.

Claims (10)

1. A polycarbonate-terminated polyurethane prepolymer is characterized in that the polyurethane prepolymer is completely terminated by cyclic carbonate groups.
2. The cyclocarbonate-based end-capped polyurethane prepolymer of claim 1, wherein the prepolymer has the following structural formula:
Figure FDA0002618396680000011
wherein the content of the first and second substances,
R1represents a small molecule or a large molecule chain segment contained in the polyol except for the terminal hydroxyl;
R2represents a hetero atomAlkyl or cycloalkyl or aryl or aralkyl groups contained in cyanate ester;
R1and R2At least one NCO group;
subscript n represents the number of repeating units contained in the generated prepolymer;
the two-sided five-membered rings represent cyclic carbonate groups.
3. The cyclocarbonate-based end-capped polyurethane prepolymer of claim 2,
the polyol is one or a mixture of two or more of micromolecular polyol, polyether polyol, polyester polyol, polyolefin polyol and vegetable oil polyol;
the isocyanate is diisocyanate or polyisocyanate.
4. A method for preparing a polycarbonate-terminated polyurethane prepolymer is characterized in that,
the preparation method adopts the following raw materials: polyol, diisocyanate or polyisocyanate, a blocking agent containing cyclic carbonate groups and hydroxyl groups in a molecule at the same time, and a catalyst;
the mass percentage of the raw materials is as follows:
Figure FDA0002618396680000012
the preparation method comprises the following steps:
step A, respectively dehydrating polyhydric alcohol and a sealing agent under the conditions of vacuum and heating;
step B, mixing polyol and diisocyanate or polyisocyanate according to a preset molar ratio, stirring at a first preset temperature under the protection of atmosphere for prepolymerization reaction, adding a catalyst, stirring at a second preset temperature for prepolymerization reaction, and obtaining a polymer with an end group of isocyanate-NCO;
and C, adding a dehydrated blocking agent into the polymer obtained in the step B to obtain a polymer which does not contain-NCO groups and has a terminal group of a cyclocarbonate group.
5. The method for preparing a cyclocarbonate-based end-capped polyurethane prepolymer according to claim 4, wherein the raw materials adopted in the method further comprise: and C, a chain extender, wherein the chain extender accounts for 0-5% of the total mass percentage, and the chain extender is added before the addition of the sealing agent in the step C.
6. The method of claim 4, wherein the cyclic carbonate group-terminated polyurethane prepolymer is prepared by reacting a cyclic carbonate group-terminated polyurethane prepolymer,
the preparation method adopts the following raw materials: the active diluent accounts for 0-30% of the total mass;
the preparation method further comprises the following steps:
and D, adding an active diluent into the polymer obtained in the step C and stirring to obtain a cyclocarbonate-based end-capped polyurethane prepolymer.
7. The method for preparing a cyclocarbonate-based end-capped polyurethane prepolymer according to any one of claims 4 to 6, wherein the polyol is one or a mixture of two or more of small molecular polyol, polyether polyol, polyester polyol, polyolefin polyol and vegetable oil polyol.
8. The method of claim 7, wherein the cyclic carbonate group-terminated polyurethane prepolymer is prepared by reacting a cyclic carbonate group-terminated polyurethane prepolymer,
the small molecular polyol comprises trimethylolpropane, glycerol, trimethylolethane, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, sucrose, sorbitol, pentaerythritol, triethanolamine and diethanolamine;
the polyether polyol comprises polyoxypropylene polyol PPG with the average molecular weight of more than 400, polyoxyethylene polyol PEG, polyoxybutylene polyol, polymer polyol, polytetrahydrofuran PTMEG and polyether polyol copolymer;
the polyester polyol comprises conventional polyester polyol with the average molecular weight of more than 400, polycaprolactone polyol and polycarbonate diol;
the polyolefin polyol comprises hydroxyl-terminated polybutadiene HTPB with the average molecular weight of more than 400, hydroxyl-terminated polybutadiene-acrylonitrile HTBN, hydroxyl-terminated styrene-butadiene liquid rubber and hydrogenated hydroxyl-terminated polybutadiene;
the vegetable oil polyol comprises castor oil polyol, soybean oil polyol and palm oil polyol.
9. The method of preparing a cyclic carbonate-based end-capped polyurethane prepolymer as claimed in any one of claims 4 to 6, wherein the diisocyanate or polyisocyanate is selected from one or more of toluene diisocyanate TDI, diphenylmethane diisocyanate MDI or liquefied MDI, isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, dicyclohexylmethane diisocyanate HMDI, xylylene diisocyanate XDI and polymethylene polyphenyl isocyanate PAPI.
10. A method for using a polycarbonate-based end-capped polyurethane prepolymer, which is characterized in that the polyurethane prepolymer of any one of claims 1 to 3 is used for toughening epoxy resin.
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